652 GEOLOGY AND TOPOGRAPHY OF THE LEAD REGION. 



OHAPTEE II. 

 TOPOGKAPHY AND SUEFACE GEOLOGY. 



TOPOGRAPHY. 



General Features of the Country. Unlike most regions wliicli 

 nature has selected for the reception of metallic ores and useful min- 

 erals, the Lead region bears no evidences of any sudden disturbances, 

 or violent action of physical forces. The effects produced by igneous 

 and eruptive agencies are wanting. Faults and dislocations of strata 

 are nowhere found. The only irregularities are slight upheavals, or 

 bending of the strata (and these never of great extent), producing 

 changes of but a few feet from the normal dip. 



Between the geological condition and the general surface contour 

 of the country, there is no direct correlation. The existence of a hill 

 or a valley on the surface is not due to a subterranean elevation or 

 depression of the surface, as is by many supposed, and whatever irreg- 

 ularities exist, must be chiefly attributed to the milder natural agen- 

 cies now constantly at work; such as running water, frost, winds, etc., 

 acting through an immensely long period of time. 



Drainage. The most marked and persistent feature of the Lead 

 region is the long dividing ridge, or watershed, which, commencing 

 near Madison, continues almost directly west to the Blue Mounds, a dis- 

 tance of about twenty miles. Here it takes a slight bend to the south- 

 west for fifteen miles, until it reaches Dodgeville, where it resumes its 

 westerly course until it terminates in the bluffs at the confluence of the 

 Wisconsin and Mississippi rivers; its total length is about 85 miles. 

 Two points are noticeable; one is, its general uniform directness of 

 outline (it being subject to but few and unimportant flexures); and 

 the other is its parallelism with the Wisconsin river, so long as the 

 latter holds an approximately westerly course; the summit of the 

 ridge being always about fifteen miles from the river. 



The divide maintains an average elevation of about six hundred 

 feet above Lake Michigan, and is seldom less than five, or more than 

 seven hundred, except at the Blue Mounds, where it gradually rises east 



